The invention relates to a logic element for representing the OR function. Such an element has two inlets for feeding in a fluid, an outlet, and a sealing device made from an elastic material which is displaceable under the action of the fluid in order, as desired, to bring about a connection between one or other inlet and the outlet.
Flow mechanisms representing the logic OR function are already known and the normally used logic symbol is: ##STR1##
This symbol represents that a signal can only be obtained at output S if a signal is present in either x or y. It is necessary from the operational standpoint for a sealing member to be placed between the two inlets x and y which prevents any connection between the said two inlets if a signal is present either in x or y and which permits the output of a corresponding signal when the particular input signal is present in x or y.
In the conventionally used sealing members, inlets x and y are separated by means of various devices which can be subdivided into two basic types, plates and membranes. Each of these types, which fulfil their function in a positive manner, has certain disadvantages. These disadvantages result in particular from the fact that the heretofore known sealing devices function only at high or only at low operating pressures, but not at pressures of intermediate values. Thus, such logic elements cannot be freely interchanged.
FIG. 1 is a simplified representation of a logic OR element of a heretofore known first type, having a plate-like sealing device. There are shown 1 as the inlet x, 3 the inlet y and 2 the outlet S. The sealing device is itself designated by the reference numeral 4.
Generally, and at least in the most widely used types, the sealing device is a disk which largely comprises an elastic or plastics material of a suitable thickness which ensures a continuous and reliable displacement of the sealing device from one sealing point 5 to the other 6.
In response to the pressures which build up on one or other side of the sealing device due to a signal appearing in x or y, the device 4 moves until it comes into contact with opening 5 or 6 and there exerts a sealing action which prevents any connection between inlets 1 and 3, while the connection between the uncovered inlet 1 (or 3) and outlet 2 remains open.
In the same way, FIG. 2 shows in simplified form a logic form OR element with a sealing device 4' in the form of a membrane. The symbols and reference numerals are the same as in FIG. 1. The difference mainly relates to the sealing 4' which comprises a membrane of generally elastic material suspended on a plurality of filaments 7 whose function is to give the sealing device the necessary flexibility and response sensitivity. Under the thrust action of the fluid entering at 1 or 3, the connection between the two inlets 1 and 3 is interrupted and the connection is produced between the relevant inlet 1 (or 3) and the outlet 2. As opposed to disk-type devices, devices provided with membranes have a higher sensitivity, which permits an operation at much lower pressures, while not, however, permitting the maximum pressures possible with the disc-type devices.
Logic elements of the previously known types which are shown in FIGS. 1 and 2 have, as indicated hereinbefore, certain disadvantages.
On examining the sealing device 4 of FIG. 1 and particularly its construction with respect to the operation of the complete element, it is clear that the sealing device 4 in the form of the above-mentioned disk must have a certain thickness permitting a correct and operationally reliable displacement between the two sealing points 5 and 6. The main disadvantage of such a device is the necessity of a relatively high minimum operating pressure in order to ensure the reliable movement of disk 4 from one position to the other and for ensuring the sealing action on applying the disk to one or other of the sealing points 5, 6.
This operating pressure, below which it is only possible with difficulty to achieve a reliable operation, is generally about 2 bar 2.0.times.10.sup.5 pascal. Parallel to this, the elements require for their sealing device a relatively large displacement path compared with the dimensions of those elements. In this there is sought a certain constructional miniaturisation when realising the OR function. However, the presence of a displacement of a by no means negligible magnitude limits the operating frequency, which is one of the most important characteristics in such elements. Furthermore, the necessity of using relatively high pressures solely because of the movement means that at the end of its movement the disk strikes the sealing edge at a high velocity, which in the case of prolonged operation can lead to surface wear, indentations in the disk (accompanied by the impairing of the sealing action) and fractures. Therefore, in the case of certain elements based on the same principle, the elastic material of the disk has been replaced by a synthetic material and sealing points 5 and 6 have been moved onto the actual disk, the sealing action being ensured by the pressure of the existing sealing edges on a flat surface. However, this solution requires a high quality for the surface and necessitates absolute reliability in the construction of the sealing edges, leading to higher manufacturing costs and difficulties in mass production.
The element shown in FIG. 2 is able to reach much higher frequencies, due to the greater flexibility, and therefore, sensitivity of membrane 4'. In addition, the element has the possibility of operating at very low pressures, but this advantage is counterbalanced by the unsuitability for operation at industrial pressures, which would lead to rapid destruction of the membrane. Thus, the possible uses are limited, and it is in particular necessary to take special technical measures when planning circuits.